The specific plan of this research proposal is to identify important mutagenicity/toxicity test systems along with the corresponding currently employed analysis procedures and subject them to a thorough evaluation from a statistical perspective. The main goal of this research is to improve the reliability and efficiency of such health related research by improving the statistical validity of the analysis procedures and by determining the optimal design configurations for performing the experiments. Preliminary efforts in this direction suggest that such improvements can generally be made resulting in better test performance (fewer false conclusions) and less expensive experiments (reduced sample size requirements).